Adding Attic Insulation With Poor Vapour Barrier

[Industrial Toys]

I need to insulate my attic. It's long, long overdue. I wished I could have used blown rock wool which I am told is not available anymore. So I will probably go with blown cellulous. The light fluffy one, not the shredded (dusty) newspaper kind.

The original glass bats were of the tar paper lined variety, so not a great vapour barrier.

Is this going to be an issue?

Oh, I should add. This is in a Northern climate, half year heating season.

Thanks in advance.

 

[bigtiller]

I don't think a vapor barrier is necessary in the ceiling. The walls need one, but if there is one in the ceiling, how will the moisture get out?

My house was built in '98 without one in the ceiling and with blown in fiberglass insulation.

 

[teejk]

I don't think a vapor barrier is necessary in the ceiling. The walls need one, but if there is one in the ceiling, how will the moisture get out?

My house was built in '98 without one in the ceiling and with blown in fiberglass insulation.

That vapor barrier debate seems to be one that will go on forever (kinda like whether coffee is good or bad). Actually not sure which side is winning right now.

 

[jack707]

Coffee and tea are good for you.

 

[Larry Caldwell]

A coat of paint will provide a good vapor barrier if it has a membrane surface, like semi-gloss or eggshell. Flat latex is a lousy vapor barrier. You can also buy vapor barrier paint that is specifically formulated for that purpose. All major paint manufacturers offer vapor barrier paint. You may have to go to a paint store rather than Home Depot to find it.

 

[Qapla]

Have you considered having icynene sprayed in/on?

 

[EddieWalker]

The vapor barrier on the walls of a house is more for wind then anything else. Cold air gets through the siding and pretty much makes cancels out any benefit from the insulation. Since heat and cold go up and down, not sideways, wind is your biggest concern with a vapor barrier.

For attic spaces, gaining the desired R rating is all that matters. You will find ceiling bats with a vapor barrier on one side, all four sides and not on it at all. I think that's more for installation then any measurable improvement to heating and cooling a house. I personally like Attic Cat a lot for blowing in insulation. There is no need for a mask, it's super easy to load the machine, it never clogs up and it's easy enough to have just about anybody help you keeping it loaded while you handle the hose.

Home Depot gives you the machine to use for free when you buy ten bags of insulation. Each bag is a lot more then the other brands, but when you figure out the math comparing coverage, it's all pretty much the same. Here in Texas, heat is our main concern, but it does get down into the teens in the winter and we can go all week and never get above 30. We also get snow here, but not very much and it never lasts very long. Our standard is now R60, which is just under 2 feet thick.

When I did my parents house, it was brand new and it took me close to 6 hours to do 3,000 sq ft. That's a long time to be in an attic, but I was never bothered by the insulation, just tough on your back, feet, ankles and legs walking around on rafters that long. Most houses that I do, it's usually about 3 to 4 hours since they already have some insulation in there.

 

[teejk]

The vapor barrier on the walls of a house is more for wind then anything else. Cold air gets through the siding and pretty much makes cancels out any benefit from the insulation. Since heat and cold go up and down, not sideways, wind is your biggest concern with a vapor barrier.

For attic spaces, gaining the desired R rating is all that matters. You will find ceiling bats with a vapor barrier on one side, all four sides and not on it at all. I think that's more for installation then any measurable improvement to heating and cooling a house. I personally like Attic Cat a lot for blowing in insulation. There is no need for a mask, it's super easy to load the machine, it never clogs up and it's easy enough to have just about anybody help you keeping it loaded while you handle the hose.

Home Depot gives you the machine to use for free when you buy ten bags of insulation. Each bag is a lot more then the other brands, but when you figure out the math comparing coverage, it's all pretty much the same. Here in Texas, heat is our main concern, but it does get down into the teens in the winter and we can go all week and never get above 30. We also get snow here, but not very much and it never lasts very long. Our standard is now R60, which is just under 2 feet thick.

When I did my parents house, it was brand new and it took me close to 6 hours to do 3,000 sq ft. That's a long time to be in an attic, but I was never bothered by the insulation, just tough on your back, feet, ankles and legs walking around on rafters that long. Most houses that I do, it's usually about 3 to 4 hours since they already have some insulation in there.

I think the debate comes in with "too tight" houses (I think they call it "sick house syndrome"). My shop has a metal ceiling and there it was necessary to have the vapor barrier to prevent rusting from above. Other than that I don't really know where the debate stands right now. Btw, on the shop people forgot to put in the "stops" on the eave edges that are an integral part of the air flow (eaves to ridge vent). We banked it up with 2 layers of thick batts...got to R50 with special order stuff and filled in the field with blown in. Was 30x40 and I think I paid the guy $1,000. Trusses are 8' OC (with 2x4 nailers). That's a little more gymnastics for this old body.

 

[Industrial Toys]

Thanks.

Yes. I have spent too much time in attics, being in the security bus. Rich people have bigger attics these days then the size of my house. They arn't too bad, except you don't want to compress their insulation, and always get insulation on their fancy clothes which is where the attic hatch usually seems to be.

I just envisioned the moist warm air migrating up through my meager fiberglass bats and condensing in the new layer of blown in insulation. I know the old fiberglass pink is useless when wet.

 

[topbuilder]

I need to insulate my attic. It's long, long overdue.

I have never used vapor barriers used in attics. But, this is Texas.
The blown is good. It will make a dusty mess into a completed home. They usually have a minimum charge, for our area it's $500. I recently did a remodel where I had to tear out about a bunch of ceiling. So that had to be insulated and I had some some R13 batts over a previous room addition that needed to be brought to R30 +. My scheduled blow guy did not make it by my deadline and I ended up laying r30 batts, no paper. $250 for insulation and a couple hours work. The think I don't like about the blow in is if there is any foot traffic afterwards, there goes your R value. Trapped air is what you are looking for.

 

[PILOON]

Up here in Quebec code is to completely seal the complete house with vapor barrier. We tape all joints and many builders even go so far as caulking stud pairs.
Outside walls are laid on strips of foam so that air can not get in under the the walls.

Most are building to a year 2000 code.
A code test is to pressurize the entire house and it has to maintain a certain pressure to pass and then the contractor gets code rated to brag about.
Also only a licensed carpenter can work on a building site and contractors need to be licensed as well.
One can expect 2-3 visits on any construction site at any time.

Window holes are now using a 3" sticky membrane to get a total seal.
Naturally we now need to add an air exchange system in order to get fresh air.
Like bring in cold outside air to replace that expensive heated inside air. LOL
It is all 'code'.
We also wrap the whole outside with Tyewrap with all taped joints.
More and more contractors are foaming all the foundation insides rather than wool batts and many use 2" dense foam boards nailed in place with furring strips.
\In any case most will shoot 2" of foam in the spaces between floor joists where the joists sit on the foundation rather than stuffing with wool.

On the other hand I have done rehabs on older buildings that the entire walls were simply filled with sawdust.
I also have had to replace log cabin logs that were rotted out, now that's fun with the chain saw being your main tool. Splicing and fitting followed by staining/aging so that it is not apparent is quite the fun.
Then I once sand blasted an entire 40 x 40 ft log cabin to bring it back to like new. (That's how you find rotted logs, LOL)

Things sure change, and costs sure climb.

 

[Billrog]

Vapor barrier is important walls and ceilings the underside of roofs where there is colder climate will develop mold on the under side of the roof without it. A properly sized furnace, ducting and cold air intake deal with fresh air circulation in the home maintaining a positive pressure.

 

[wawajake]

to the original poster............please be careful taking advice from southern climates where the opposite impacts of heating and cooling have opposite needs in regards to vapour barrier ....the vapour barrier needs in colder climates like our Canada...........even differ between southern Ontario and Northern Ontario . Here is a good website that has various advice in regard to insulation, air barriers and yes and vapour barriers. This link opens on basements (because that was what I was researching) but has tons of university articles on side drop downs on the website about all areas of our northern houses. .
Preventing mold when you insulate your basement | Green Home Guide | Ecohome

 

[Industrial Toys]

Thanks

I know, I have felt bad going into peoples attics trampling down the insulation. I try and be carefull and even try and fix it, but that seems almost futile.

I can't seem to get the blown mineral stuff I like, and don't care for the dust of cellulous. Maybe, I will just go with bats, even though I know it won't make a nice blanket.

 

[teejk]

Thanks

I know, I have felt bad going into peoples attics trampling down the insulation. I try and be carefull and even try and fix it, but that seems almost futile.

I can't seem to get the blown mineral stuff I like, and don't care for the dust of cellulous. Maybe, I will just go with bats, even though I know it won't make a nice blanket.

Maybe instead of a single batt you go with 2 layers and criss-cross them.

 

[Industrial Toys]

Not a bad idea. I am also concerned about making cosy mouse housing. At least with bats, I don't have to get and return a blower which could be 45 minutes away, one way! A good part of the day, in all.

Just thinking about it. I could probably do a good portion of the job in bats, just in the time it takes to get and return the blower.

Save the money on the blower

Get non itchy bats

Be able to do future work . . . and

Not have to build dams for the blown insulation.

Maybe the choice is obvious.

 

[teejk]

Not a bad idea. I am also concerned about making cosy mouse housing. At least with bats, I don't have to get and return a blower which could be 45 minutes away, one way! A good part of the day, in all.

Just thinking about it. I could probably do a good portion of the job in bats, just in the time it takes to get and return the blower.

Save the money on the blower

Get non itchy bats

Be able to do future work . . . and

Not have to build dams for the blown insulation.

Maybe the choice is obvious.

Not so sure you need the "non-itchy" variety, rather just get it done, take a shower and wash your clothes! When you think about it the "criss cross" method might leave a few small holes where the batts intersect but cut on the ground and put in place goes quickly....more expensive but you eliminate that settling problem and lessen the "critter" problem.

 

[topbuilder]

Thanks

I know, I have felt bad going into peoples attics trampling down the insulation. I try and be carefull and even try and fix it, but that seems almost futile.

I can't seem to get the blown mineral stuff I like, and don't care for the dust of cellulous. Maybe, I will just go with bats, even

though I know it won't make a nice blanket.

The BEST way would be to scoop out the existing, lay the R30 in the joist run and then use the left out blow in on top. Of course that is also the most labor intensive... I have never had issues with itching for more than an hour or two. A dust mask is good idea. Not the cheap ones, get the ones you can actually pull air through.

I have a house I'm starting in a couple weeks. My insulator tells me the code has changed to R38 in attics. We might be going foam though making it irrelevant.

 

[teejk]

The BEST way would be to scoop out the existing, lay the R30 in the joist run and then use the left out blow in on top. Of course that is also the most labor intensive... I have never had issues with itching for more than an hour or two. A dust mask is good idea. Not the cheap ones, get the ones you can actually pull air through.

I have a house I'm starting in a couple weeks. My insulator tells me the code has changed to R38 in attics. We might be going foam though making it irrelevant.

Around here R50 is now code on the ceilings. For some reason they don't care about walls much (other than the sill plates in the basement which I guess is now up to 2" foam) but I guess that says heat loss is not a big deal there. Been working with 2 contractors on a house my MIL bought to be closer...biggest problem has been to get them to show up (hence contractor #2) but that's a different story. One would think that we would have some "consensus" on best practices but the 2 are worlds apart...one is traditional (minimal foam), the new guy is a foam nut.

 

[sailfast]

Two words
Spray foam